1. Field of the Invention
The present invention relates to mechanical heat transfer systems, and more particularly to a comprehensive and versatile heat exchanger and heat pump and related apparatus for, among other things, selectively cooling domestic air space and/or heating domestic and/or swimming pool water.
2. Description of the Background Art
Mechanical heat pump systems are well known in the art for absorbing heat from one medium and transferring the heat to another medium. In a conventional mechanical refrigeration system a pair of heat exchangers are fluidly connected in a refrigeration circuit, through which a cooling or heating medium (hereinafter "refrigerant") flows. According to the circulation direction of the refrigerant, one heat exchanger functions as an evaporator and the other heat exchanger functions as a condenser.
A common commercial embodiment of mechanical refrigeration is found in residential and commercial air conditioning systems. Such systems may be either "packaged" wherein all of the necessary components are packaged in a single unit, or "split" systems wherein the evaporator is separated from the compressor and condenser.
Furthermore, the need for heating domestic potable and swimming pool water is well recognized in the prior art. In warm climates the use of a swimming pool may be limited to those months where the ambient temperature is sufficient to warm the swimming pool water to a comfortable level. In colder climates, swimming pool water must be continually heated in order to provide comfortable aquatic recreation. In addition, there exists a number of other needs and uses for warmed water including domestic hot water and water used for irrigation.
A number of references are directed to providing a mechanical system capable of heating a water source. For example U.S. Pat. No. 5,560,216, issued to Holmes, discloses a combination air conditioner and pool heater. U.S. Pat. No. 4,688,396, issued to Takahashi, discloses an air conditioning hot-water supply system. U.S. Pat. No. 5,184,472, issued to Guilbault et al., discloses an add on heat pump swimming pool control. U.S. Pat. No. 4,667,479, issued to Doctor, discloses an apparatus for heating, cooling and dehumidifying the enclosure air from an indoor swimming pool while simultaneously heating or cooling the pool water. U.S. Pat. No. 4,279,128, issued to Leniger, discloses a swimming pool heating system which utilizes a pump that is used for heating heat transfer fluid which is circulated through the primary coil of a heat exchanger.
U.S. Pat. No. 4,232,529, issued to Babbit et al., discloses a mechanical refrigeration system for selectively heating swimming pool water. Babbit et al. discloses three operating modes for selectively transferring heat. In the first mode, heat is transferred from the atmosphere to pool water. In the second mode, heat is transferred from a conditioned space to the atmosphere. In the third mode, heat is transferred from the conditioned space to pool water.
U.S. Pat. No. 4,019,338, issued to Poteet, discloses a heating and cooling system for heating pool water while providing means for cooling or heating the interior of a building. Poteet discloses a system including a compressor connected through suitable conduits to a first condenser located in a swimming pool, a second condenser, and an evaporator located in a conditioned space.
However, there are a number of inherent disadvantages present in the prior art systems. Specifically, the prior art systems fail to disclose pool water heat exchangers having means for preventing heat exchanger corrosion. In particular, when water flow in prior art refrigerant-to-water heat exchangers is interrupted, air pockets may form in high points within the tubing system. When this happens, chlorine gas escapes from the pool water and cohabits the air pockets. It has been found that accelerated corrosion of the metallic heat exchanger surfaces, such as copper-based metals, occurs at the interface of the chlorine gas, pool water, and copper tubing, leading to failure of the system. It is apparent that active corrosion occurs at an accelerated rate along boundary lines separating fluid and gas resulting in a measurable electrical voltage generated by corrosion which consumes the host metal. Over time, the copper tubing experiences repeated insult at the boundary layer where the tubing, air, and water intersect, resulting in an electrochemical half-cell effect which generates an electrical voltage while consuming the copper tubing. The problem is most pronounced in refrigerant-to-water heat exchangers wherein at least a portion of the water therein drains away from high points during periods when the circulating pump is de-energized, leaving an "air gap" in the highest point(s) in the pool water conduits. The repeated insult which occurs at the interface of the pool water/chlorine gas/copper tubing surface is driven by the half-cell effect which creates a voltage, in turn consuming the copper. Ultimately, such corrosion causes failure of the heat exchanger tubing, thereby causing loss of refrigerant and further allowing water to contaminate the refrigerant system resulting in catastrophic system failure. Thus, for a system to be sufficiently reliable and commercially feasible, there still exists a need for a heat transfer system having a corrosion resistant heat exchanger.
In addition, the presence of multiple heat transfer coils in heat exchangers having varying capacities, in a common refrigeration system, results in system problems in connection with maintaining and balancing the refrigerant charge. This problem is further compounded in system configurations wherein there is substantial distance between the various components (i.e., long conduit runs).
Furthermore, other systems fail to disclose control schemes that maximize energy efficiency by minimizing pool water pumping requirements in association with system operation. In addition, the systems of the background art fail to disclose the use of multiple thermostatic set-points for maximizing use of the refrigerant-to-water heat exchanger as a condenser thereby resulting in increased system efficiency. The present invention is directed toward overcoming these and other disadvantages in the prior art.